Multiple stage cascaded triggered vacuum gap devices



Dec. 5, 1967 J. M. LAFFERTY 3,356,894

ED TRIGGERED VACUUM GAP DEVICES MULTIPLE STAGE- CASCAD Filed Oct. 14, 1966 /n vemor James M Lafferfy',

Pulse Source PU/SE Source i v His Afforney.

United States Patent 3,356,894 MULTIPLE STAGE CASCADE!) TRIGGERED VACUUM GAP DEVICES James M. Latferty, Schenectady, N.Y., assignor to General Electric Company, a corporation of New York Filed Oct. 14, 1966, Ser. No. 586,751 5 Claims. (Cl. 315-111) This application is a continuation-in-part of my copending application, Ser. No. 535,948, filed Mar. 21, 1966.

The present invention relates to improved high power, high current triggered vacuum gap devices, particularly adapted to switch high currents at exceedingly high voltage ranges by the cascading of two or more triggered vacuum gap stages in a unitary evacuable envelope.

With the recent developments in triggered vacuum gap devices such as is set forth in my US. Patent No. 3,087,- 092, issued Apr. 23, 1963, and entitled, Gas Generation Switching Tube, devices of this type have proven to be exceedingly useful in the switching, interruption and general control of high power electric circuits.

The present trend in development for such devices, which already exhibit great reliability, rapid response time, low jitter, and other desirable characteristics, is to extend the current and voltage ratings at which such devices may be operated.

Accordingly it is an object of the present invention to provide triggered vacuum gap devices suitable for operation at high currents in the hundredths of thousands of ampere ranges and suitable for withholding much greater voltages than heretofore could be withheld by such de- 1 vices.

A further object of the present invention is to provide triggered vacuum gap devices capable of operating at very high voltages without increasing the size of the devices correspondingly.

Yet another object of the present invention is to provide triggered vacuum gap devices wherein a plurality of independent triggered vacuum gap stages may be cascaded and connected in series for operation at exceedingly high voltage ratings.

In accord with one feature of the present invention I provide a triggered vacuum gap device having a single unitary evacuable envelope containing a pair of independent unitary triggered vacuum device stages which are serially connected electrically and so disposed that the production of an electron-ion plasma between the respective electrode members of one triggered vacuum gap stage provides for the injection of an electron-ion plasma into the inter-electrode gap of a closely disposed, other triggered vacuum gap stage to cause the breakdown thereof, with the resultant operation of both sections in series, without the attendant increase in size which would be required to hold ofi. same voltage.

More specifically, I provide, in one embodiment of the invention, an evacuable envelope having at either end thereof a trigger gap for the injection of an electron-ion plasma into an inter-electrode space each of which interelectrode spaces comprises a first, outer electrode assembly having a cylindrical configuration including a pair of radially disposed inwardly depending relatively thin electrode vanes and a second, inner electrode assembly including a plurality of radially disposed outwardly depending thin vanes, the second, inner electrode assemblies of each of the closely disposed triggered vacuum gap stages being electrically connected in series and mechanically juxtaposed so as to facilitate the free passage of electron-ion plasma from one set of electrode assemblies to the other. This juxtaposition causes the ionization of the inter-electrode spacing, of one trigger vacuum gap stage to propagate electron-ion plasma into the inter-elec- 3,356,894 Patented Dec. 5, 1967 trode space of the other triggered vacuum gap stage to cause the near-instantaneous breakdown thereof.

The novel features believed characteristic of the present invention are set forth in the appended claims. The invention itself, however, together with further objects and advantages thereof may be more readily understood by reference to the appended drawings in which:

FIGURE 1 is a vertical cross-section of a two stage cascaded triggered vacuum gap device constructed in accord with the present invention,

FIGURE 2 is a horizontal cross-sectional view taken through section lines 22 of the device of FIGURE 1,

FIGURE 3 is an enlarged cross-sectional View of the trigger electrode assembly utilized in each of the triggered vacuum gap sections of the device of FIGURE 1, and,

FIGURE 4 is a schematic diagram of a means for connecting the device of FIGURE 1 in a circuit alternative to that illustrated in FIGURE 1.

In my copending application, Ser. No. 535,948, filed Mar. 21, 1966, the disclosure of which is incorporated herein by reference thereto, I disclose high power vacuum gap discharge devices which in one embodiment, as for example, that illustrated in FIGURE 1, comprises a triggered vacuum gap device having a pair of electrode assemblies, one of which is comprised of a cylindrical body with a plurality of inwardly depending radial vanes of relatively thin cross-section and large area, the other of which comprises a plurality of centrally disposed outwardly depending thin radial electrode vane members which are inter-digitally located with respect to the inwardly depending members of the first electrode vanes.

While this device is highly successful for the interruption, switching and other control functions with respect to electric currents and voltages and other controlling of high power, high voltage electric circuits, there is a limitation upon the voltage which may be held off and this limitation is dependent upon the size of the device and the spacing between the more closely disposed sections of the inter-electrode gap, as for example the closest portions between the outer, inwardly disposed, vanes and the inner, outwardly disposed, vanes. Although the hold-off voltage of such devicesmay be increased by increasing the size thereof, I have found that the hold-01f voltage (that voltage which may be safely applied across the device Without causing the electrical breakdown thereof by areing between the electrodes) does not increase as the interelectrode spacing increases, as would be the case if the size of the device were merely increased. Rather, as the inter-electrode spacing increases the hold-otf voltage increases but at a less rapid rate or, a less than linear rate. Additionally as the size of the device is increased and as the inter-electrode spacing increases, the difliculty in causing the breakdown thereof and the necessity of increasing the amount of energy to be supplied by the trigger mechanism concomitantly increases.

Accordingly I have found unexpectedly that the hold off voltage of triggered vacuum gap devices in accord with the present invention may not only be increased at a greater rate than by increase in the size but that the energy necessary to cause the breakdown of the devices may be maintained at a comparable value by providing a plurality of independent ganged or cascaded triggered vacuum gap stages closely juxtaposed so as to cause the breakdown of one by an appropriately applied trigger electrode assembly to cause the near-simultaneous breakdown of the other or others.

FIGURE 1 of the drawing illustrates a device constructed in accord with the present invention which includes a two stage cascaded triggered vacuum gap assembly including two serially connected trigger vacuum gap sections. In FIGURE 1, an evacuable envelope, represented generally as 1, includes a pair of cylindrical insulating envelope members 2 and 3 disposed coaxially to one another and connected to an annular ring electrode support member 4 by a pair of annular flanged ceramicto-metal seals 5 and 6. The ends of evacuable envelope 1 are closed by a pair of apertured cup members 7 and 8, each of which is fastened to the respective juxtaposed cylindrical insulating body by an annular collar 9 and an annular metal-to-ceramic sealing flange 10. A trigger electrode assembly 11 is disposed within the aperture in cup 7 and hermetically sealed thereto and a trigger electrode assembly 12 is disposed within the aperture of end cup 8 and hermetically sealed thereto. A trigger electrode lead wire 13 is used to supply an electrical signal to trigger electrode assembly 11 and a similar trigger electrode lead 14 supplies a signal to trigger electrode assembly 12. Each of trigger electrode leads 13 and 14 is passed in insulating relationship through trigger electrode assembly 11 or 12 through respective insulating bushings 15 and 16.

The members enclosed within that portion of envelope 1 generally encompassed by cylindrical insulating member 2 constitute a first trigger electrode stage represented generally by and the members enclosed within that portion of evacuable envelope 1 including the volume encompassed by cylindrical insulating member 3 constitutes a second trigger electrode assembly represented generally by 30. First trigger electrode stage 20 includes an outer electrode assembly 21 including a cylindrical outer member 22 and a plurality of relatively thin extended-area inwardly depending radial fins 23 which are parallel to the longitudinal axis of the device of FIGURE 1, which axis may be described as a line passing through the central portions of trigger electrode assemblies 11 and 12 about which the cylindrical insulating members 2 and 3 are concentric. A second electrode assembly 24 within trigger stage 20 includes a plurality of outwardly depending thin, relatively large area radial vanes 25. Pins 25 are disposed so as to be interposed between adjacent fins 23 of electrode assembly 21 and equidistant from adjacent ones thereof. The length thereof is substantially the same length of the inwardly depending vanes 23 of outer electrode assembly 21. Electrode assembly 24 is mechanically and electrically connected to an annular support member 26 at the lower portions thereof which annular support member is in turn electrically and mechanically connected to an supported by annular member 4 which constitutes a portion of the evacuable envelope 1. At the same point that annular support member 26 joins support member 4, support member 4 also is jointed by a short cylindrical annular shield member 27, the prime purpose of which is to prevent the pamage of metallic particles out from the inneraction space so as to short-circuit the insulating cylinder 2 by causing the coating thereof with metallic particles. Although this shield member is shown as being relatively short, it may be of any desired length and configuration sufficient to shield insulator 2.

The construction of the second triggerable vacuum gap stage of the device of FIGURE 1 represented generally by 30 is substantially identical with that of first stage 20 and like elements thereof are indicated by the corresponding numeral in the 30 series to those elements indicated in the 20 series in first trigger gap stage 20 of FIGURE 1. In the illustration of FIGURE 1 in first stage 20 the inwardly depending outer radial vanes are shown in full section and the outwardly depending in radial vanes are shown in partial section. In stage 30, on the other hand, the inner outwardly-depending electrode vanes are shown in full view and the outer inwardlydepending vanes are shown in partial section. A plasma transfer tube, 40, which is a cylindrical member is connected between inner electrode support members 26 and 36 and is electrically connected to the inner electrode assemblies 24 and 34. It presents an open, unimpeded path for the conduction of electron-ion plasmas between the interaction spaces of stages 20 and 30 during operation.

Means are provided by contacts 41 and 42 to provide connection for an electrical load circuit to be interrupted, switched, or otherwise controlled by the operation of the triggerable vacuum gap device of FIGURE 1. A pair of capacitors 43 and 44 constituting a voltage divider network having a center tap at 45 connected to electrode support member 4 is connected between the load connectors 41 and 42. Means for applying a triggering pulse to trigger electrode assemblies 11 and 12 are provided by a pair of separate, but simultaneously controlled, pulse sources 46 which are connected to the associated trigger electrode lead 15 or 16 and to end conduction discs 9.

In FIGURE 2 of the drawing a horizontal plan view taken along lines 22 of FIGURE 1 clearly shows the juxtaposition of the inner electrode assembly 24 having outwardly disposed radial vanes 25 and outer electrode assembly 21 having inwardly disposed radial electrode vanes 23. Also visible is shield member 27 and insulating cylinder 2.

In FIGURES 1 and 2 the preferred structural materials of the various illustrated constituents are substantially the same as the materials as is set forth in great detail in my aforementioned copending application. For example, members 2 and 3 are a high voltage insulator as, for example, a fosterite ceramic Pyrex glass or high density alumina. Electrode assemblies 21, 24, 3'1, and members 26, 27, 36, and 37 and '34 are made of extremely high purity, preferably zone-refined material, as for example, copper, having less than one part in 10 of gas or gasforming impurities, particularly oxygen or oxygen-forming impurities. The other metallic members as for example end cap members 9 and 10 and support member 4 should be constructed of high purity metals, as for example, copper, stainless steel or nickel which are outgassed to preclude the presence of concentrations of gas or gas-forming materials but need not have the extremely high purity of the electrode materials themselves. Before operation the device is evacuated to a pressure of 10 mm. Hg or less to obtain the high hold-oif and rapid recovery characteristics of vacuum.

In operation, it shall be assumed that the device is to be used to switch from a non-conducting to a conducting condition between a high voltage applied between terminals 41 and 42. With the voltage applied between terminals 41 and 42, the voltage divider comprising capacitors 43 and 44 causes a division of the applied voltage between the two series inter-electrode gaps of stages 20 and 30. Thus, for example, approximately half the applied voltage is across the capacitor 44 and similarly is applied across the vanes of electrode assemblies 21 and 24. The remaining half of the applied voltage is across capacitor 43 and similarly is applied across the vanes of electrode assemblies'31 and 34.

When it is desired to fire the device and cause the voltage between terminals 41 and 42 to be short-circuited or switched, a predetermined control causes a positive pulse of from 50 to 5,000 volts, for example, depending upon the magnitude of the voltage being held off and the dimensions of the inter-electrode gaps between the primary electrode assemblies, to be applied to trigger electrode leads 14 and 13, respectively. If the applied line voltage is a unidirectional voltage, only one of the primary arc electrodes 21 or 31 associated with the two trigger assemblies 11 and 12 will be negative and a positive trigger voltage applied to the trigger associated with the negative electrode causes a trigger breakdown between that electrode assembly and the trigger anode of the associated trigger assembly. 'If, on the other hand, the

voltage applied to terminals 4 1 and 42 is an alternating voltage, one of the two primary electrode assemblies 21 or 31 is more negative than the other and the associated trigger assembly, either 11 or 12, will break down, causing the injection of an electron-ion plasma into the inter electrode space between the associated primary electrodes. Assuming the initial breakdown occurs in the interaction gap between electrode assemblies 21 and 24, a pulse of ion-electron plasma is injected into the inter-electrode spacing between electrode assemblies 21 and 24 causing the establishment of a high voltage are therebetween. Upon the establishment of the arc, the charge upon capac itor 44 discharges through its connections to the respective electrodes, thus preventing the extinction of the arc and permitting the establishment of a diffuse are over the wide area of the narrow vanes 24 of electrode assembly 25 and 23 of electrode assembly 21. Upon the establishment of the full arc across the inter-electrode gap between electrode assemblies 21 and 24 the electron-ion plasma generated thereby is propelled through arc transfer tube and into the inter-electrode spacing between the vanes of the electrodes of triggered gaps section 30, namely electrode assembly 31 and 34. With the establishment of the are between the electrodes 21 and 24, substantially the entire voltage between terminals 41 and 42 is transferred across capacitor 43. With this high voltage applied across the electrodes 31 and 34 in the presence of the electron-ion plasma propelled thereinto from triggered vacuum gap section 20, an arc is established between electrode assemblies 31 and 34 within a matter of less than a microsecond after the initial breakdown of gap section 20. Upon the establishment of an are between electrode assemblies 31, 34, the charge upon capacitor 43 dischargesthereacross and the circuit is complete from terminal 41 through the spacing between electrode as se-mblies 2'1 and 24, then through the are between electrode assemblies 31 and 34 and finally out to terminal 42, with the voltage distributed substantially evenly between the two arcs and the erosion upon any given are electrode being no greater than it would be if it were the only are between the arc terminals.

Thus, in the operation of the device in accord with the present invention and the cascading of the plurality of arc-electrodes and trigger vacuum gap stages, one upon another, it is possible to hold off higher voltages because the voltage held off is distributed evenly as the number of the gaps is increased.

In FIGURE 3 of the drawing there is illustrated a typical vacuum gap trigger assembly which may be utilized in accord with the present invention. This gap is disclosed and described in greater detail in my copending application, Serial No. 580,998, filed September 21, 1966, and assigned to the present assignee, the disclosure of which is incorporated herein by reference thereto, of which it is one preferred embodiment. It follows, however, that other suitable trigger electrode assemblies such as the other assemblies illustrated in the aforementioned copending application may be utilized and that the exact trigger electrode assemblies utilized will depend upon the values of the operating parameters present.

In FIGURE 3 the trigger electrode assembly :11 comprises a trigger anode 48 in the form of a molybdenum cup which rests upon a ceramic annular washer 49 having a coating thereupon of an ionizable substance-producing film which is scored with an annular groove 50 to produce a pair of thin film rings 51 and 52 which are electrically insulated from one another, separated by groove 50, which constitutes the trigger gap. Film 51 is in electrical and mechanical contact with trigger anode 48 and film 52 is in electrical and mechanical contact with the trigger cathode member 53, which is in the form of an inwardly tapered nozzle member which overlaps the inner dimension of annular ceramic disc 49 and protects trigger gap 50 from line of sight contact with the interaction space between the primary gaps of the trigger vacuum gap stage with which it is connected. Trigger electrode member 53 is electrically and mechanically connected within the aperture within upper cylindrical cup-shaped member 7 of FIGURE 1 of the drawing and is in electrical and mechanical contact with the disc-shaped upper portion of electrode assembly 2 1 so that the voltage applied to the outer electrode assembly of trigger vacuum gap stage 20 is also applied to trigger cathode 53.

Trigger anode 48 is supported resiliently within assembly 47 by means of insulating ceramic disc 54 held in spring tension with a refractory metallic spring 55 which abuts upon a sealing flange 56 which connects the insulating bushing 15 through which anode lead 13 passes for connection with trigger anode 48. An annular reentrant flange 57 is in hermetic seal with member 56 and is suitably welded, brazed, or otherwise connected in hermetic seal to cylindrical end member 58 which is likewise hermetically sealed with a suitable weld, braze or other connection to member 7.

In operation, the trigger cathode 53 is at the same negative potential as outer electrode assembly 21 and a pulse of positive voltage is applied through trigger anode lead 13 to trigger anode 48 and to film 51. Electrical break down occurs between films 51 and 52. Films 51 and 52 may either be a suitable active gas storing medium, as for example, a titanium or rare earth hydride loaded with hydrogen which is discharged upon the establishment of a trigger arc therebetween or conveniently may be composed of a high vapor pressure, low melting point material, as for example, copper or beryllium, as set forth in my copending application, Ser. No. 516,942, filed December 28, 1965, the disclosure of which is incorporated herein by reference thereto, and assigned to the assignee of the present invention. Upon the establishment of a trigger are an electron-ion plasma is generated by the injection and ionization of ionizable material from films 51 and 52. As the volume Within the trigger electrode is filled, this electron-ion plasma is propagated through the throat of the trigger cathode 53 and projected into the interaction space between the primary arc-electrode assembly 21 and 24 to cause electrical breakdown thereof.

In FIGURE 4 of the drawing there is shown a circuit for an alternative breakdown sequence for the device of FIGURE 1. In the circuit of FIGURE 4 no external trigger source need be supplied and breakdown may be caused to occur upon the application of a transient overvoltage or a trigger pulse which may be superposed upon the line voltage normally applied across the device. In FIGURE 4 the applied voltage of the line is applied between terminals 41 and 42. Assuming a trigger pulse or an overvoltage, transient applied to the line, spark breakdown occurs across gaps 63 and 64, which are connected across the electrode assemblies 21 and 24 and the assemblies 31 and 34, respectively, with gaps 63 and 64 being in series with resistance65 and 66, ,67 and 68. Trigger anode lead 13 is connected to the common terminal between resistance 65 and 66. Trigger anode lead 14 is connected to the common terminal between resistances 67 and 68. Upon the application of an over-voltage, spark gaps 63 and 64 break down. Current is then conducted between the terminals .41 and 42 through trigger anode 13, resistance 65, gaps 63 and 64, resistance 67 and trigger anode 14. Depending upon which terminal 41 or 42 is more negative one of trigger anodes 13 or 14 will participate in a trigger assembly breakdown, causing the breakdown of either stage 20 or 30. Assuming stage 20 is broken down because terminal 41 is more negative, the current flow will then be through electrode assembly 21, are 69, assembly 24, gap 64, resistance 67 and trigger anode 14. With the entire line voltage across resistance 67 and plasma injected into stage 30 from stage 20, stage 30 breaks down in less than a microsecond and the entire device is broken down. The generalized concept of the resistive divider circuit for successively triggering oppositely disposed trigger electrode assemblies in a single-gap device is not my invention but is the invention of S. R. Smith and is disclosed and claimed in his copending application, assigned to the assginee of the present invention. Resistance 66 may be of the order of 30,000 ohms and is used to reduce the voltage to the trigger electrode, and under transient initial arcing conditions, to limit its current. Similarly resistance 65, which may conveniently be of .the order of 50 ohms, is used as a current limiting resistance through the spark gap 63. With the breakdown of section 20 the entire line voltage is thrown across section 30, which thereupon breaks down, causing current to flow as is described with respect to the previous embodiment of FIGURE 1 and the entire device is operative with the same results as is described with respect to FIGURE 1.

While the invention has been described hereinbefore with respect to two trigger gap stages, it is readily apparent that any number of stages may be connected in series without departing from the inventive concept herein. Thus, for example, the device may be broken along the line 3-3 and two such elements mated together, back to back, to provide a four gap device with a trigger assembly at either end. Or it may be broken along the line 3-3 and 44 to provide an intermediate section having no trigger electrode assemblies associated therewith which may be interposed between other section such as 20 and 30 having trigger electrode assemblies associated therewith. Thus, any even number of stages may readily be utilized to provide a trigger vacuum gap device having a plurality of separate gaps in series with a corresponding increase in the hold-off voltage which may be used in connection with the device without increasing the size, other than in length, and without increasing the inter-electrode spacing nor increasing the energy necessary to pulse the device to cause operation thereof for switching, interruption or other control functions in electric power circuits.

While the invention as set forth hereinbefore has been described with respect to particular embodiments thereof, many modifications and changes will readily occur to those skilled in the art. Accordingly by the appended claim I intend to cover all such modifications as may fall within the true spirit and scope of the present invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A multi-stage high voltage triggered vacuum gap device comprising:

(a) an hermetically sealed envelope evacuated to a pressure of 10- mm. of mercury or less and including at least one portion constructed of a high voltage insulator to separate different sections thereof from one another electrically (b) a plurality of stages of vacuum gaps arranged in series along a common longitudinal axis within said envelope, each of said stages containing a pair of primary arc-electrode assemblies defining therebetween a primary breakdown gap (c) means interconnecting one of the primary electrode assemblies of each stage to a primary electrode assembly of an adjacent stage to place the primary gaps of adjacent stages electrically in series circuit relationship;

(d) are transfer means for facilitating the passage of an electron-ion plasma generated by arcing in one of said stages into the primary gap in an adjacent stage to cause electrical breakdown thereof,

(e) a pair of trigger electrode assemblies closely disposed to the primary breakdown gap of one of said stages at either end of said series array to cause initial breakdown thereof,

(f) means for connecting a load to voltage in circuit with said device, and

(g) means for applying a triggering signal to said trigger assemblies to cause operation of said device.

2. The device of claim 1 wherein each of said stages comprises a first outer primary electrode assembly including a plurality of inwardly depending thin radial vanes and a second inner electrode assembly including a plurality of outwardly depending thin radial vanes interdigitally disposed between the vanes of said first electrode assembly.

3. The device of claim 2 wherein adjacent stages are interconnected in series circuit relationship by electrically connecting the inner electrode assemblies of two adjacent states.

4. The device of claim 3 wherein further adjacent stages are inerconnected in series circuit relationship by electrically interconnecting the outer electrode assemblies of other adjacent stages.

5. The device of claim 1 wherein a trigger electrode assembly is associated with the primary inter-electrode gap of the stage at each end of the plural stage array.

References Cited UNITED STATES PATENTS 2,948,831 8/1960 Stoelting 315-36 3,046,436 7/1962 Cavalconte 313149 DAVID J. GALVIN, Primary Examiner.

STANLEY D. SCI-ILOSSER, Examiner. 

1. A MULTI-STAGE HIGH VOLTAGE TRIGGERED VACUUM GAP DEVICE COMPRISING: (A) AN HERMETICALLY SEALED ENVELOPE EVACUATED TO A PRESSURE OF 10-5 MM. OF MERCURY OF LESS AND INCLUDING AT LEAST ONE PORTION CONSTRUCTED OF A HIGH VOLTAGE INSULATOR TO SEPARATE DIFFERENT SECTIONS THEREOF FROM ONE ANOTHER ELECTRICALLY (B) A PLURALITY OF STAGES OF VACUUM GAPS ARRANGED IN SERIES ALONG A COMMON LONGITUDINAL AXIS WITHIN SAID ENVELOPE, EACH OF SAID STAGES CONTAINING A PAIR OF PRIMARY ARC-ELECTRODE ASSEMBLIES DEFINING THEREBETWEEN A PRIMARY BREAKDOWN GAP (C) MEANS INTERCONNECTING ONE OF THE PRIMARY ELECTRODE ASSEMBLIES OF EACH STAGE TO A PRIMARY ELECTRODE ASSEMBLY OF AN ADJACENT STAGE TO PLATE THE PRIMARY GAPS OF ADJACENT STAGES ELECTRICALLY IN SERIES CIRCUIT RELATIONSHIP; (D) ARC TRANSFER MEANS FOR FACILITATING THE PASSAGE OF AN ELECTRON-ION PLASMA GENERATED BY ARCING IN ONE OF SAID STAGES INTO THE PRIMARY GAP IN AN ADJACENT STAGE TO CAUSE ELECTRICAL BREAKDOWN THEREOF, (E) A PAIR OF TRIGGER ELECTRODE ASSEMBLIES CLOSELY DISPOSED TO THE PRIMARY BREAKDOWN GAP OF ONE OF SAID STAGES AT EITHER END OF SAID SERIES ARRAY TO CAUSE INITIAL BREAKDOWN THEREOF, (F) MEANS FOR CONNECTING A LOAD TO VOLTAGE IN CIRCUIT WITH SAID DEVICE, AND (G) MEANS FOR APPLYING A TRIGGERING SIGNAL TO SAID TRIGGER ASSEMBLIES TO CAUSE OPERATION OF SAID DEVICE. 